“We found that about 3.6 per cent of the cancers worldwide – or nearly half a million new cancer cases a year – were caused by excess body weight,” Dr Pandeya said.

“In Australia, the percentage is similar, with 3.4 per cent of all cancers in men (2350 new cases) and 7.4 per cent (3782 new cases) in women diagnosed in 2012 attributable to overweight and obesity.”

Researchers looked specifically at cancers where being overweight or obese is a proven risk factor.

“Of these cancers, we found that, for men, 23 per cent of kidney cancers, 19 per cent of colon cancer and 13 per cent of pancreatic cancer could be attributed to excess weight.”

Dr Pandeya said the impact was more pronounced in women.

“Post-menopausal breast cancer and endometrial cancer were responsible for more than 60 per cent of cancers due to obesity in women diagnosed in Australia in 2012,” she said.

“That’s more than 2000 cases.”

According to the latest figure, about 63 per cent of Australians are overweight or obese.

Using estimates of the number of overweight and obese people in the population and the proven increased risk of cancer, researchers determined how many new cancer cases could be attributed to the world’s increasing body mass index levels, which have doubled since 1980.

The global study found that the burden of cancer was strongest in the developed world, with the US leading the way.

Dr Pandeya said the findings highlighted the need for more concerted efforts to curtail the rates of overweight and obesity.

“Other important risk factors for cancer, such as smoking, are declining, but we see the proportion of overweight and obese men and women still rising in most countries,” she said.

“If this trend continues we are likely to see an increasing number of people diagnosed with cancers that could have been avoided by maintaining a healthy weight.”

Dr Pandeya is joint lead author, with IARC’s Dr Melina Arnold, on the research paper, which is published in The Lancet: Oncology.